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Biol 240 (micro) > Topic 2: Bacteria > Flashcards

Topic 2: Bacteria Flashcards

1
Q

Spherical

A
  • spherical or round
  • COCCUS
    -found in various habitats, including soil, water and human body
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2
Q

Rod-shaped

A
  • e. coli
  • BACILLUS
  • commonly found in soil, water, and the human intestine
  • use gliding motility
    • cells joined together in a smooth, unbranched filament, trichomes)
  • can also grow in branching filaments (hyphae) (clump= mycelia)
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3
Q

Comma shaped

A
  • curved
  • VIBRIO
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4
Q

Spiral-shaped

A
  • bizarre shapes, like telephone cords
  • move like corkscrews, rotating clockwise or counterclockwise to go forward or back
  • works well in aquatic environments, will find them
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5
Q

Variable

A
  • cant quite identify as having one shape
  • called pleiomorphic, multiple shapes
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6
Q

Why can decreasing cell size be an advantage for bacteria?

A

a higher surface to volume ratio means a greater rate of nutrient/waste exchange, higher metabolic rate, faster growth rate and evolution

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7
Q

Bacteria that are exceptions to the typical size

A

Thiomargarita namibiensis
Epulopiscium fishelsoni

-both can reach close to a millimeter in length
- advantage of being big, can store more things, inclusion bodies

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8
Q

Things in bacterial cytoplasm (11)

A

DNA nucleoid
Chromosome-packaging proteins
Enzymes involved in synthesis of DNA, RNA
Regulatory factors
Ribosomes
Plasmid(s)
Enzymes involved in breaking down substrates
Inclusion bodies
Gas vesicles
Magnetosomes
Cytoskeletal structures

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9
Q

DNA Storage

A

Nucleoid
- largest region in cell
- no membrane surrounds it
- house chromosomes and DNA replication machinery
-uses several mechanisms to reduce space

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10
Q

Inclusion Bodies

A

accumulations of carbon, nitrogen, sulfur or phosphorus storage compounds
- sulfur globules: store sulfur for energy
- polyhydroxybutyrate (PHB): carbon storage compound

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11
Q

Gas vesicles

A

Used for buoyancy control

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12
Q

Carboxysomes

A

location of carbon fixation reactions (using RuBisCO enzyme)

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13
Q

Magnetosomes

A

associated with direction-finding

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14
Q

Topoisomerase

A

modify structure of DNA to enable “super
coiling”

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15
Q

Bacterial Cytoskeleton

A
  • keeps everything in right place
  • proteins involved in cell wall synthesis (cell division):
    *MreB: defines cell shape
    *FtsZ: forms ring for cell division
  • proteins involved in moving internal items
    *Par homologues: separate newly replicated chromosomes
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16
Q

Cell envelope

A

all layers surrounding the cytoplasm of cells
- cytoplasmic membrane
- cell wall
- outer membrane if present

17
Q

Cell membrane

A

GENERAL
- All cells have a cytoplasmic membrane
- Separates the interior of the cell from the external environment
STRUCTURE
- Usually composed of a phospholipid bilayer with embedded proteins
- Hydrophobic core
- Hydrophilic surfaces interact with either the external environment or the cytoplasm
- Chemically variable due to changes in fatty acid groups attached to a glycerol backbone
- Connected by ester linkages
- May have sterol-like molecules called “hopanoids” in it to help with stability across temperature ranges
OTHER
- capture energy
- holding sensory systems

18
Q

Cell Wall

A
  • give cells their shape
  • protect them from osmotic lysis/ mechanical forces
  • structure: matrix of crosslinked strands of peptidoglycan subunits
  • peptidoglycan subunits:
  • N-acetylmuramic acid (NAM)
  • N-acetylglucosamine (NAG)
  • short peptide chain

Peptides and peptide crosslinks vary by species

19
Q

Peptide crosslinks features

A
  • NAM connects to NAM
  • Unusual D-isomers of amino acids in the crosslinks
  • Diaminopimelic acid (DAP) in Escherichia coli
  • Pentaglycine interbridges within Staphylococcus aureus
20
Q

Formation of bacteria cell walls

A
  • Bactoprenol transports pentapeptide precursors
  • Transglycosylation attaches NAG to NAM
  • Transpeptidation connects peptide chains
21
Q

Gram+ Bacteria

A
  • thick outer layer of peptidoglycan
  • variable width periplasmic space
  • negatively charged teichoic acids in the peptidoglycan
22
Q

Gram- bacteria

A
  • very thin layer of peptidoglycan
  • periplasmic space of varying width
  • outer membrane composed of lipopolysaccharide (LPS)
23
Q

Gram Stain

A

Crystal violet stains cells
Iodine traps the colour
Alcohol decolourization shrinks large pores in Gram-positive cells and locks crystal violet stain in
Alcohol strips away some outer membrane lipids in Gram-negative cells
Safranin stains Gram-negative cells pink

24
Q

Outer Membrane

A

LPS in Gram-negative outer membrane
- O (outer) side chain of polysaccharides can vary
- Changed by the microbe to evade host immune responses
- Must be careful when treating Gram-negative infections because outer membrane may cloak components that elicit a strong immune response (e.g., Lipid A)

25
Q

Facilitated diffusion

A

involves a protein associated with the cytoplasmic membrane enabling a substrate or solute to pass down its concentration gradient into the cell, doesn’t require ATP

26
Q

co-transport

A

2 types
Symport: brings something of low concentration in with something of high concentration
Antiport: something with high concentration inside the cell, bring in something with low concentration outside the cell, no ATP required

27
Q

active transport

A

uses ATP
transports solutes into cell against concentration gradient using energy from ATP

28
Q

How do antibiotics target bacteria?

A

B-lactam inhibits FtsI transpeptidation, interrupting covalent linkages between neighboring peptide chains (in the bacteria, stops cell wall formation)

29
Q

What is some bacteria’s response to antibiotics, how is that resolved?

A
  • some bacteria produce b-lactamase, interfere with the lactam ring, destroys the b-lactam, so resistant to antibiotic
  • resolved by adding clavulanic acid (isn’t antibiotic itself), interferes with and occupies b-lactamase, so b lactam can do its job
30
Q

Flagella

A
  • spiral, hollow, semi-rigid filaments extending from the cell surface
  • locations and number vary across species
  • three pieces: filament of flagellin proteins, hook protein, basal body
  • energy comes from proton motive forces
31
Q

Motility of flagella

A
  • Polar flagella: propel forward or backward depending on spin direction
  • Amphitrichous: propel one way or another depending on which flagellum spins
  • Peritrichous: one direction of rotation moves forward, a change in direction induces a tumble
32
Q

Chemotaxis

A

-run and tumble
- either towards chemical attractants or away from repellents

33
Q

Gliding motility

A

smooth sliding over a surface

34
Q

Twitching motility

A

slow, jerky process using pili that extend, attach to, and pull along a surface

35
Q

Pili

A
  • fibers of pilin protein, possess other protein on their tips for sticking
  • extend outward from cell, allow attachment and twitching motiliy
36
Q

Stalks

A
  • A “holdfast” of polysaccharides is used to attach an organism to a surface
  • Provide extra surface area for nutrient absorption
37
Q

Capsules

A

Thick layer of polysaccharides surrounding some cells: adhesion (e.g., biofilms), defense against host immunity, protection against desiccation

38
Q

Surface arrays (S-layers)

A
  • Crystalline array of interlocking proteins
  • Protects cell against predation or infection with bacteriophages
  • Found in Gram-positive and Gram-negative cells

Biol 240 (micro) (10 decks)

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